An administrator can take advantage of the international spam feature of EOP to block messages written or sent from certain countries.
The process to block messages from certain countries/languages is performed on the content filter layer of EOP protection, which means that the header and message body of the message will be taken in consideration.
In order to configure, we must be logged on the Exchange Admin Center of a tenant with Office365 or EOP service. Click on Protection andt then Content Filter. Select Default and click on Edit.
In the new page, click on international spam and on the right side we have the option to enable messages written or messages sent from the defined countries. To add a country to the list on either option, just click on Add.
The following list will be displayed and the administrator has to double click on each country/language that you want to block at EOP level, after defining, click on OK and then save.
How can I check the existent messages to see their language and country?
Before applying the feature you may want to do some research to check where the messages are coming from and if they will match the security that you are planning to configure on EOP. You can use your own external messages to check it out, basically you need to get the Internet Headers of any external messages, and since that message was received by EOP, then a X-Forefront-Antispam-Report will be added to the message and there are two fields that identify country and language, which are CTRY: e LANG: as show in the message below.
If you don’t want to spend too much time looking at the header you can always use EXRCA.com and that information will be displayed on the second section. We wrote a Tutorial about the step by step how to get the Internet Headers from Outlook and using EXRCA, you can check it out here: http://itprocentral.com//why-it-is-taking-so-long-to-receive-a-message-in-my-exchange-server/
It is really simple to block messages by country/language using EOP, however we live in a global society and check if the but we live in a global community and you may be surprised to find out that a country that you have never heard before , so before applying this protection make sure that your organization does not perform business with those countries.